Association of poor adherence to guideline-directed medical treatment with adverse events including fatal arrhythmia in heart failure with reduced ejection fraction: A nationwide cohort analysis

Abstract Background Poor adherence to guideline-directed medical therapy (GDMT) in patients with heart failure with reduced ejection fraction (HFrEF) is associated with increased risks of mortality and hospitalization. However, its association with malignant arrhythmic events and aborted sudden cardiac death (SCD) remains less well defined, particularly among patients with implantable cardioverter-defibrillator (ICD) or cardiac resynchronization therapy with defibrillator (CRT-D) for primary prevention. Methods We analyzed data from the Korean National Health Insurance Service between 2008 and 2020 and identified patients who had ICD or CRT-D implanted for primary prevention. Those with prior sustained ventricular tachycardia (VT), ventricular fibrillation/flutter (VF/VFL), or aborted SCD device before implantation were excluded. Adherence to renin-angiotensin system blockers (RASB), beta blockers (BB), and mineralocorticoid receptor antagonists (MRA) was assessed using a weighted proportion of days covered (PDC) and categorized as optimal (≥0.8), suboptimal (0.6-0.8), and poor (